为了探索煤层巷帮大直径预卸压钻孔在工作面超前支承压力等增量静载加载条件下的防冲卸压效应, 采用理论分析、室内试验以及数值模拟等方法, 对采动增量静载加载条件下煤层卸压钻孔响应规律及其极限性进行了研究。理论分析结果表明, 静载加载下, 大直径钻孔二次调整, 破裂区和塑性区发生扩展变化, 降低了增量静载的集中程度, 但随着加载程度的升高, 破裂区煤体逐渐塌落, 碎胀后充满整个钻孔, 自由变形补偿空间减小, 并约束塑性区的扩展, 卸压能力逐渐减弱。室内试验结果表明, 钻孔煤样峰值强度与加载速度具有明显的正相关性; 输入的弹性能和加载速度成正相关; 耗散能与加载速度成负相关。数值模拟结果表明, 随着静载加载速度及应力集中程度的增加, 钻孔卸压区范围和卸压幅度逐渐减小, 钻孔围岩塑性区体积逐渐减小, 卸压区内的峰值弹性能逐渐升高, 钻孔耗散弹性能的能力降低; 引入卸压幅度、应力增幅以及弹性能储能率3个指标, 分析了大直径钻孔的响应卸荷极限性。研究结果可为类似条件下的钻孔卸压方案设计提供参考。

To explore the anti-scouring and pressure relief effects of large-diameter pre-destress boreholes in coal roadway under incremental static loading conditions, such as advanced support pressure in working face, theoretical analysis, laboratory experiments and numerical simulations were used to study the response law and limit of coal seam pressure relief boreholes under mining incremental static loading conditions. Theoretical analysis results show that under static loading, the secondary adjustment of large-diameter boreholes causes expansion and changes in both fracture and plastic zones, reducing the concentration of incremental static load. However, the coal body in fracture zone gradually collapses as the loading degree increases, and after fragmentation and expansion, it fills the entire borehole, reducing the compensation space for free deformation and constraining the expansion of the plastic zone, resulting in a gradual weakening of the pressure relief capacity. The laboratory test results show that there is a significant positive correlation between the peak strength of drilled coal samples and the loading speed. The input elastic energy is positively correlated with the loading speed. The dissipated energy is negatively correlated with the loading speed. The numerical simulation results show that as the static loading speed and stress concentration increase, the range and amplitude of borehole pressure relief zone gradually decrease, the volume of plastic zone of the borehole surrounding rock gradually decreases, the peak elastic energy in the pressure relief zone gradually increases, and the ability of the borehole to dissipate elastic energy decreases. The response unloading limit of large-diameter boreholes was analyzed by introducing three indicators: pressure relief amplitude, stress amplification, and elastic energy storage rate. The research results can provide reference for the design of drilling pressure relief schemes under similar conditions.